Acute Renal Injury (ARI), also known as acute renal failure (ARF) or acute kidney injury (AKI), is a serious medical condition of the kidneys. ARI is characterized by a decline of glomerular filtration rate, urine output, or both. ARI is accompanied by an inflammatory response that if unchecked can lead to renal fibrosis and chronic renal failure. ARI usually occurs over a period of hours or days and is potentially reversible. ARI is a common complication in hospitalized patients, and its incidence has risen significantly in the past 15 years. A particular type of ARI, contrast-induced nephropathy, is caused by the toxic effects of some radiocontrast agents.